1. Field of the Invention
The present invention relates to an electrode for electrolytic dressing grinding, more particularly to a removable electrode whose surface can be exchanged in a short time.
2. Description of the Related Art
In recent years, with development of scientific technique, a demand for superfine processing has rapidly escalated, and as mirror surface grinding means for satisfying the demand, an electrolytic in-process dressing grinding method (ELID grinding method) has been developed, and presented by the present applicant, et al. (xe2x80x9cTrend of Latest Technique of Mirror Surface Grindingxe2x80x9d of Riken symposium held on Mar. 5, 1991).
As schematically shown in FIG. 1, the ELID grinding method includes: using a conductive grinding wheel 1 instead of an electrode in conventional electrolytic grinding; disposing an electrode 2 opposite to the grinding wheel via a gap; passing a conductive liquid 3 through between the grinding wheel and the electrode while applying a voltage to between the grinding wheel 1 and the electrode 2; dressing the grinding wheel by electrolysis; and simultaneously grinding a workpiece by the grinding wheel. That is to say, in the grinding method, the metal bond grinding wheel 1 is used as an anode, the electrode 2 disposed opposite to the surface of the grinding wheel via the gap is used as a cathode, and electrolytic dressing of the grinding wheel is performed simultaneously with a grinding operation, so that grinding properties can be maintained and stabilized. Additionally, in FIG. 1, reference numeral 4 is a workpiece (material to be ground), 5 is an ELID power supply, 6 is a power supply member, and 7 is a nozzle of the conducive solution.
In this ELID grinding method, even when an abrasive grain is fine, the grinding wheel is dressed through electrolytic dressing and prevented from being clogged. Therefore, with the fine abrasive grain, a processed surface remarkably superior like a mirror surface can be obtained by a grinding process. Therefore, in the ELID grinding method, sharpness of the grinding wheel can be maintained both of highly efficient grinding and mirror surface grinding, and the method is expected to be applied to various grinding processes as means able to create a highly precise surface in a short time, which has been impossible in a conventional art.
In the aforementioned ELID grinding, a metal component of a grinding wheel bonding material is deposited on the surface of the cathode 2 disposed opposite to the metal bond grinding wheel 1 as the anode based on an electric plating principle, contrary to an anode reaction which is electrolytic eluation of the grinding wheel bonding material.
Since the deposit on the surface of the cathode has a composition close to that of a pure metal in principle, conductivity is not lost. However, when the ELID grinding process is performed over a long time, following problems would occur. 1. The gap between the cathode and the grinding wheel is filled with the deposit, the surface of the electrode becomes irregular, and electrolytic dressing of the grinding wheel becomes unstable. 2. A sufficient amount of grinding solution cannot steadily be supplied after a long time. To solve the problems, in the conventional art, the apparatus would be stopped every several days (about one to seven days), a distance between the electrode and the grinding wheel is enlarged, or the electrode is removed from the apparatus, and the deposit sticking to the surface of the electrode is removed with a sand paper or the like. As a result, however, following other problems would occur. 3. An apparatus maintenance time is lengthened, continuous operation is limited and operating efficiency is deteriorated. 4. After repeated maintenance, an electrode surface shape changes, the entire electrode needs to be exchanged, much time is therefore required for changing the electrode and readjusting the entire apparatus, and the operating efficiency is further deteriorated. Consequently, an ELID grinding effect cannot be maintained during continuous unmanned operation, and it has been recognized that these problems have to be overcome for complete automatic operation.
The present invention has been developed to solve the problems. That is to say, an object of the present invention is to provide an electrode for electrolytic dressing grinding, in which even with a deposit built up on a cathode surface the cathode surface can be cleaned in a short time, even after repeated use an electrode shape does not change, and an ELID grinding apparatus can therefore steadily be operated in an unmanned manner for a long time.
According to the present invention, there is provided a removable electrode for electrolytic dressing grinding in which the electrode is disposed opposite to a processing surface of a conductive grinding wheel via a gap, a conductive liquid is passed through the gap to apply a voltage to the gap, the grinding wheel is dressed by electrolysis and a workpiece is simultaneously ground, the electrode comprising: an electrode support member (12) having a surface (12a) disposed opposite to the processing surface of the grinding wheel via a constant gap; a conductive foil (14) detachably attached to and along the opposite surface of the electrode support member; and a conductive terminal (16) for contacting the conductive foil to apply the voltage to the conductive foil.
According to the aforementioned constitution of the present invention, since the electrode support member (12) is provided with the opposite surface (12a), the conductive foil can be disposed opposite to the processing surface of the conductive grinding wheel via the gap simply by attaching the conductive foil (14) to and along the opposite surface. Therefore, in this state, it is possible to perform the electrolytic dressing grinding (ELID grinding) by applying the voltage to the conductive foil via the conductive terminal (16), passing the conductive liquid through between the conductive foil and the conductive grinding wheel, dressing the grinding wheel by electrolysis, and simultaneously grinding the workpiece.
Moreover, the conductive foil (14) is detachably attached to the opposite surface of the electrode support member. Therefore, even when the deposit is built up on the electrode surface, the electrode surface can be cleaned in a short time simply by changing the conductive foil. Furthermore, even when the conductive foil is repeatedly exchanged, the electrode shape does not change, so that the ELID grinding apparatus can steadily be performed in the unmanned manner for the long time.
According to a preferred embodiment of the present invention, the conductive foil (14) is applied to the opposite surface (12a) in a single layer or laminated layers.
When the conductive foil is of the single layer, the conductive foil can be exchanged and the electrode surface can be cleaned only by stripping the conductive foil (14) from the electrode support member (12) and attaching another new conductive foil to the electrode support member. Moreover, when the conductive foil is of multiple layers, the surface conductive foil with the deposit thereon is simply stripped from the multiple layers, and the underlying conductive foil is in turn disposed opposite to the processing surface of the conductive grinding wheel via the gap, so that ELID grinding can be performed.
When the conductive foil (14) is formed in a tape shape, the conductive foil is preferably intermittently or continuously moved along the opposite surface (12a).
In this constitution, a portion of the conductive foil with the deposit built up thereon can intermittently or continuously be replaced with a new portion on which no deposit is built up, and the ELID grinding apparatus can steadily be operated in the unmanned manner for a long time.
Furthermore, the electrode support member (12) is preferably formed of an insulating material, and may be provided with a guide groove (13) via which the conductive foil is movably guided along the opposite surface (12a).
According to this constitution, while the conductive foil (14) is disposed opposite to the processing surface of the conductive grinding wheel via the constant gap, the portion of the conductive foil with the deposit built up thereon can be replaced with the new portion via the guide groove (13).